What is it ? Its a very important part of the gun that is probably the most confusing part in your kit.

What does it do ? It pushes the barrel forward after the gun has been fired. This returns the barrel to its forward position , ready to fire again.

Where does it go ?It sits in the bottom of the receiver with the long tube part facing towards the barrel on the left side viewed from the rear of the firearm.(cocking handle would be on right side).

How does it attach ?There are two bolts used to mount the recuperator to the receiver.
The first is a normal looking bolt that has small flats on its underside of its head. This bolt is used in the rear rectangular opening of the recuperator body. It protrudes out the bottom of the receiver behind the gripstick mounting pin and is secured by a 10-32 nut with a diameter of 9MM.
The second bolt is very unusual in appearance , it has a head with a long and short side. this head fits into the opening on the tube of the recuperator to secure the barrel plunger in to the tube against the spring pressure. The threaded part of this " T " bolt protrudes through the left side of receiver just behind the camming piece where its secured by a 10-32 nut with a diameter of 9MM on the outside.
pictures of these bolts are available below CHECK FOR WELD BUILD UP IN THE CAM AREA BINDING THE PLUNGER BEFORE INSTALLING RECUPERATOR

What are the different types ?Well , the obvious two are the original " MG42/M53 type " without a tail after the rear section and the latter " MG3 type " with the tail.
The less obvious are small differences in spring strength and shape of barrel plunger head.

Are they compatible ? YES and NO, There are no real differences between an MG42 recuperator and a M53 Yugo recuperator. The reports to date so far say people are having good results from whatever recuperator they received with their kit ( 8MM or .308) as long as it is assembled right and in decent condition from the start.
On the other hand the tail of the MG3 type has definite clearance issues with a MG42 unmodified receiver, and the MG42 style buffer. (click to go to buffer stickie.) .
Arrow points to tab that needs to be removed to install MG3 recuperator.Tab is part of the gripstick mount which is riveted just in front of the buffer lock cams . Aproximately .60" gap between the two.

How does that front nut get installed again ? With the long leg facing towards the butt-stock when the recuperator is in the gun.
shown the correct way on the left side in this picture.

How do i assemble it ? the following picture shows the parts lay-ed out in order they go into the tube.
Start with the small spring , then the small rod , then a keeper .
BE CAREFUL THE SPRINGS ARE DANGEROUS WHEN COMPRESSEDassembling the part is not easy to do and will require, 3 hands , two sets of safety glasses and several small screwdrivers as well as some cursing.

What modifications are required to convert the recuperator to work in a semi-auto mg42 ?

The semi-auto mg42 is required to have a block permanently installed in the receiver that prevents the use of a unmodified full-auto bolt carrier. This block requires the removal of the sear catch lugs on the underside of the full-auto bolt to clear the bolt block. This requires the recuperator to be cut to fit around the FA bolt block. Click here for more info on the bolt.

The cocking handle in a full-auto grips the sear catch lugs on the bolt carrier to charge the gun. In a semi, with the lugs removed, it is necessary to weld a tab to the right side of the bolt carrier to substitute as the original sear catch lugs for the cocking handle. This cocking tab needs enough space to be able to retract and charge the gun for firing.

It is usually required that the recuperator have the right side vertical ledge removed for this cocking " sail panel '' that you've welded to the bolt-carrier's right side .typically the recuperator is also cut back to the second rib to make room for the FA bolt block.

To disassemble the recuperator try a small flat bladed screwdriver and a pair of needle nose pliers.

starting at the topinsert screwdriver between keeper and head of plunger,push down on the plunger compressing the spring the retainer should have some freedom of movement once released from the spring tension.quickly grasp retainer with needle nose pliers and rotate 90 degrees

the retainer should be holding the plunger down under pressure at this point.you can either pull the retainer out through the "window" of the recuperator or compress the recuperator assembly by inserting a probe rod into it , this will help align the retainer in the "window" better and make it easier to pull out .

CAUTION , when the retainer is removed the pressure of the spring and guide rod will be released . hold the probe rod firmly .

"good , bad, .....I'm the man with the gun."

Its amazing anything works right around here with a bunch of over-age juvenile delinquents running the place.

You'll want:
bore cleaning rod long enough to reach end of recuperator
long needle nose pliers

First, note that the first-in plunger & spring are shorter than the others.
Second, be sure you know how to get a keeper in. Practice with just the keeper (no spring pressures). It will become obvious that it has to be put in "sideways" and rotated.

Put the shorter plunger/spring in and push all the way to the rear using the cleaning rod.

Push hard on the rod to compress spring so that the plunger head is about flush with the end of the cutout window.

With your fingers, push a keeper in sideways, pushing the rod to the side (but keep it there, and keep the pressure on!)

Remove the cleaning rod. The keeper will remain in the cutout window, albeit at the wrong angle.

Grasp the tab on the keeper with needle nose pliers. Push the cleaning rod back down the recuperator body and apply pressure to the side of the keeper. Simply twist the keeper and it will pop into place.

I have a yugo kit as well. It differs from the pic they show above but the first (what Im calling) "spring guide" is the direct sub for that part. You should have 3 of those "spring guides" and the 3 retainers to hold em. BTW I pushed the guides down and then used safety wire to keep tension on the spring. The retainers just came right out. After removing the retainers I just cut the wire (holding tension on the spring) and slowly let off tension till the spring was loose. worked great!Glenn

My Wise lite build (not quite done yet) but the barrel installation seems to bind on the recouperator instead of pushing it back against its springs. Do I need to apply more force when putting the barrel in place or add lubrication? Is there a measurement I can check to see if the end of the recoupe is in the right postion (fully forward)? The rails are in and flush against the camming section.

Railsplitter - Mine did the same thing. Be REAL SURE that the forward nut has not been installed backward. I did that one time. It allows that end piece (the one that touches the barrel) to sit too far foreward to allow the barrel to slide in. So, first, take the recoup out. If the foreward bolt is in backwards, just rotate it 90 degrees, and re-install it. You can ( I did) grind a little extra lead so the barrel pops in easier. Just do a little. That piece does not engage the barrel on a very large area to begin with. Plus, re-engeneering something that already works is not real good to try. I'll bet you've installed that forward bolt backwards (look at the above picture that someone posted). Always wear safety glasses when playing with springs. Blind dudes shooting belt-feds is really scary stuff!MGB

I reinstalled the recoup a few times and applied a little force in closing the gate - works fine. Always have issues being timid around semi auto firearms. Springs that close bolts need to move with authority not slowly or feed issues occur

Can a Mg3 recuperator be used in a Wise lite semi auto receiver since they are longer in the buffer area?

A regular recuperator rest against the tab that is part of the grip stick mount, but doesn't the MG3 recuperator rest against the buffer? If the wise lite receiver is longer in the buffer area I guess there would be a gap between the recuperator and buffer, which is probably not a good thing.

I'm just starting to learn all this MG-42 stuff, so can someone confirm or deny my suspicions?

The recouperator mounts with a bolt through the side,and one through the bottom.The extra length shouldn't affect these fixed mounting points.The front of the recoup remains in the exact spot in relation to the barrel. ---bil

"I dream of a world where I can buy alcohol,tobacco and firearms from the same drive-up window,and use them all on the way home from work!" Dogbert